A disgruntled farmer who blamed the school for his money troubles blew up the school in Bath, Mich., a small town northeast of the state capital of Lansing. That day, 38 children and six adults died.

"It's inexplicable," Bernstein said. "There's no explanation. Something in the makeup of these people makes them do it."

The farmer's name was Andrew Kehoe, and he died, as well, when he blew up his own car.

In rural American in the 1920s, it was easy to come up with explosives. Small-town hardware stores sold dynamite and other explosives to farmers to remove stumps from fields.

It was a time when one-room school districts were consolidating into larger, town schools. The 55-year-old Kehoe was enraged about a tax the community levied on itself to build the new Bath Consolidated School. His farm had gone into foreclosure, and he blamed the school.

He had access to the school - he was a board member, the treasurer, in fact. He also was the school's caretaker. Kehoe secretly placed hundreds of pounds of explosives under the school, apparently doing it over a period of months.

Historical sources say that on that Wednesday morning, Kehoe beat his wife to death and set his farm on fire. While firefighters were there, an explosion rocked the school.

Kehoe then appeared at the school. As people ran up to his car, he detonated explosives inside it, making it a 1920s version of a suicide car bomb. The shrapnel-filled car bomb killed the school superintendent and others.

Bernstein said he sees parallels between the Connecticut killings and the Bath massacre generations ago. Both Kehoe and alleged Newtown shooter Ryan Lanza had ties to the school, and both apparently killed people close to them before the school attack.

"It's eerie to me how close it is," Bernstein said.

The author said he has maintained contact with people in Bath, and he said that even generations later, the trauma is not forgotten.

"It's like it happened yesterday," Bernstein said. "One person did a lot of damage to a lot of lives. But like they did in Bath, they will come out of this in Connecticut."